expand test coverage of 'store' module.
expand test coverage of 'store' module.

marma/rdflib,dbs/rdflib,armandobs14/rdflib,armandobs14/rdflib,RDFLib/rdflib,ssssam/rdflib,dbs/rdflib,RDFLib/rdflib,armandobs14/rdflib,dbs/rdflib,RDFLib/rdflib,avorio/rdflib,avorio/rdflib,dbs/rdflib,yingerj/rdflib,avorio/rdflib,armandobs14/rdflib,avorio/rdflib,yingerj/rdflib,marma/rdflib,RDFLib/rdflib,ssssam/rdflib,marma/rdflib,ssssam/rdflib,marma/rdflib,yingerj/rdflib,ssssam/rdflib,yingerj/rdflib